Editor's note: Google isn't the only way for your business to be discovered online. This is the third in a five-part series looking at alternate sources for search.

Though it can be a great way to promote brands and products, few business owners even think of creating podcasts, which are audio files or video files that are posted online and can be downloaded by others to view or listen to. You can find podcasts to download in online marketplaces such as Apple's iTunes store.

Take for example the case study shared by Glen Allsopp of the ViperChill blog. In just six days, the first episode of his newly released podcast was downloaded more than 18,000 times, providing tremendous exposure that might've been difficult to achieve using any other advertising medium.

So if you're thinking about launching your own business podcast, how do you get a high ranking in iTunes' search feature, while maximizing your online exposure? Here are some of the factors that could help drive the best results:

Related Video:

-- Keyword-optimized content. As with Google, Bing and YouTube searches, keywords matter on iTunes. Although fewer fields in your podcast's settings can be optimized with target search engine optimization (SEO) keywords than in the YouTube channel creation area, you still have a few opportunities. For example, adding a keyword or two to your podcast's title can help your podcast to rank better in the iTunes search results, as will adding these target phrases to the description area you're allotted. There are a few caveats to keep in mind. As usual, you should avoid overdoing the optimization. Cramming dozens of repetitive keywords into every field can turn off visitors. At the same time, be wary of placing too many long-tail keywords into your podcast's title and description fields. Unlike people on the traditional search engines, iTunes users don't enter lengthy searches into the program when searching for podcasts. As an example, they're far more likely to enter the phrase "blogging" than "how to make money blogging podcast" when seeking content on this digital marketing strategy. So, keep your own target keywords simple.

-- Content quality. While the quality of your podcast's content certainly plays a role in its eventual ranking in the iTunes search results, the exact mechanisms by which this occurs aren't fully known. To satisfy any of the different qualitative assessment possibilities, make sure your podcast episodes meet the following criteria:

• Long enough to cover a single topic thoroughly (usually at least five to 10 minutes)• Well-researched and factually correct• Professionally produced without sound quality issues• High-quality overall image

If you don't have the skills needed to turn out a professional looking podcast on your own, consider outsourcing various tasks such as sound editing.

-- Number of subscribers versus casual listeners. When listeners tune into your podcast via iTunes, they have two choices -- download individual episodes from your series or subscribe to it so that new episodes are automatically added to their digital devices through the iTunes interface.

From iTunes' standpoint, your podcast's ratio of "subscribers to casual listeners" matters. A higher percentage of subscribers indicates that your content is valuable enough for people to opt in to receive it automatically. As this ratio goes up, your average position in iTunes' search results should increase as well.

To increase the number of subscribers to your podcast, don't be shy. Ask listeners to subscribe from within your podcast episodes, on your website, on your social media profiles or anywhere else you advertise your audio content.

-- Number of listener reviews and comments. iTunes also likes to see a high number of reviews and comments left on a podcast. This demonstrates that your content is interesting enough for listeners to actively engage with.

To encourage engagement, invite listeners to leave feedback on your podcast's listing page. Don't consider paying for positive reviews. It not only is dishonest, but it is not a sustainable option for long-term iTunes success.

-- Age of podcast. The age of your podcast plays a role in determining its place in the iTunes search results. Though the exact weight of this ranking factor isn't known, older podcasts tend to be higher in iTunes' listings. Unfortunately, there isn't much you can do to manipulate this ranking variable.

But this factor is important to keep in mind if you're thinking of launching a podcast. You should consider releasing a single episode as quickly as possible so you can start the clock running on your content.